Jian-Qiang Zhao

Asymmetric Michael/Cyclization Cascade Reaction of 3-Isothiocyanato Oxindoles and 3-Nitroindoles with Amino-Thiocarbamate Catalysts: Enantioselective Synthesis of Polycyclic Spirooxindoles

An unprecedented organocatalytic asymmetric Michael/cyclization cascade reaction of 3-isothiocyanato oxindoles and 3-nitroindoles has been disclosed. A wide range of enantioenriched polycyclic spirooxindoles, containing three contiguous chiral centers with two of them having quaternary stereocenters, could be smoothly obtained with satisfactory results (up to 99% yield, >99:1 dr, and 96% ee). This method is very promising because the reaction is scalable, and the versatile transformations of the products into other spirocyclic oxindoles are also feasible.

Tandem Michael Addition-Ring Transformation Reactions of 3-Hydroxyoxindoles/3-Aminooxindoles with Olefinic Azlactones: Direct Access to Structurally Diverse Spirocyclic Oxindoles

An efficient method for the direct construction of two classes of spirocyclic oxindoles by the reactions of 3-hydroxyoxindoles/3-aminooxindoles and (Z)-olefinic azlactones through a tandem Michael addition-ring transformation process has been developed. With DBU as the catalyst, a range of spiro-butyrolactoneoxindoles and spiro-butyrolactamoxindoles, containing an oxygen or a nitrogen heteroatom, respectively, in the spiro stereocenter, were smoothly obtained with good to excellent diastereoselectivities in high yields.

Zn-Catalyzed Diastereo- and Enantioselective Cascade Reaction of 3-Isothiocyanato Oxindoles and 3-Nitroindoles: Stereocontrolled Syntheses of Polycyclic Spirooxindoles

A catalytic asymmetric Michael/cyclization cascade reaction of 3-isothiocyanato oxindoles and 3-nitroindoles has been disclosed with a chiral Zn(OTf)2/diphenylamine-linked bis(oxazoline) complex as the catalyst. A range of enantioenriched polycyclic spirooxindole derivatives containing three contiguous stereocenters were efficiently constructed in quantitative yields with excellent diastereo- and enantioselectivities. Importantly, the metal catalytic strategy in this work is significantly superior to the previous organocatalytic method in the diastereo- and enantioselectivities for almost all of the examined cases.

Preparation of 3-Sulfonylated 3,3-Disubstituted Oxindoles by the Addition of Sulfinate Salts to 3-Halooxindoles

An efficient method for the preparation of 3-sulfonylated 3,3-disubstituted oxindole derivatives has been developed. The protocol involves a base-catalyzed addition of sulfinate salts to 3-halooxindoles, affording a wide range of 3-sulfonylated 3,3-disubstituted oxindoles in good to excellent yields under mild conditions. A preliminary trial of asymmetric catalytic version was conducted and gave promising enantioselectivity. The mechanism for the reaction was tentatively explored with the help of mass spectrometric analysis.

Asymmetric synthesis of β-hydroxy-α-amino phosphonic acid derivatives via organocatalytic direct aldol reaction of α-isothiocyanato phosphonates with aldehydes.

α-Isothiocyanato phosphonates are first used as nucleophiles to react with aldehydes for the asymmetric synthesis of β-hydroxy-α-amino phosphonic acid derivatives. The process is catalyzed by a quinine-derived thiourea via cascade aldol/cyclization reaction, affording a wide range of protected β-hydroxy-α-amino phosphonates containing adjacent quaternary-tertiary stereocenters in up to 93% yield, up to 81% ee, and >99:1 dr. This work represents the first example of α-isothiocyanato phosphonates serving as nucleophiles that are used in the catalytic asymmetric synthesis.

Two New Highly Oxygenated and Rearranged Limonoids from Phyllanthus cochinchinensis

A new 6/6/5/6-fused limonoid, phyllanthoid A (1), possessing both 19/30 and 19/29 oxygen bridges was isolated from Phyllanthus cochinchinensis (Euphorbiaceae), together with a new related limonoid, phyllanthoid B (2). Their structures were determined by spectroscopic analysis and single-crystal X-ray diffraction in the case of 1. Compound 1 displayed moderate antifeedant against the generalist plant-feeding insect Spodoptera exigua and cytotoxicity against the MCF-7 cell line.

Two-dimensional hydrophilic interaction chromatography × reversed-phase liquid chromatography for the preparative isolation of potential anti-hepatitis phenylpropanoids from Salvia prattii.

Traditional Tibetan medicine is important for discovery of drug precursors. However, knowledge of the chemical composition of traditional Tibetan medicines is very limited due to the lack of appropriate chromatographic purification methods. In the present work, Salvia prattii was taken as an example, and an off-line hydrophilic interaction liquid chromatography/reversed-phase liquid chromatography preparative method was developed for the purification of phenylpropanoids with high purity from a crude sample of Salvia prattii. Based on the separation results of four different chromatographic stationary phases, the first-dimensional preparation was performed on an XAmide preparative column with the crude sample concentration of 62.0 mg/mL, and five main fractions were obtained from the 12.4 g crude sample with a recovery of 54.8%. An XCharge C18 preparative column was applied in the second-dimensional preparation to further isolate the phenylpropanoids from the redissolved first-dimensional fractions with concentration of approximately 50.0 mg/mL. The purities of the phenylpropanoids isolated from the crude sample of Salvia prattii were higher than 98%, indicating that the method was efficient for the purification of phenylpropanoids with high purity from Salvia prattii. Additionally, this method showed great potential in the preparation of phenylpropanoids and can serve as a good example for the purification of phenylpropanoids from other plant materials.

Multiple Hydrogen-Bonding Bifunctional Thiourea-Catalyzed Asymmetric Dearomative [4 + 2] Annulation of 3-Nitroindoles: Highly Enantioselective Access to Hydrocarbazole Skeletons

A method for the enantioselective construction of hydrocarbazole skeletons through dearomative [4 + 2] annulation of 3-nitroindoles with Nazarov reagents is reported. The reactions use multiple hydrogen-bonding bifunctional thiourea as catalyst and are highly diastereo- and enantioselective (up to >20:1 dr and >99% ee). The protocol was demonstrated by preparative-scale experiment and the versatile conversion of the products. The multiple hydrogen-bonding in the catalyst plays a pivotal role in the reactivity and stereoselectivity.

The organocatalytic asymmetric Neber reaction for the enantioselective synthesis of spirooxindole 2H-azirines

The asymmetric Neber reaction of 3-O-sulfonyl ketoxime, in situ generated from isatin ketoxime and sulfonyl chloride, for the synthesis of chiral spirocyclic oxindole compounds is reported. With the developed protocol, a range of chiral spirooxindole 2H-azirines could be obtained in good to excellent yields and up to a 92 : 8 enantiomeric ratio by using (DHQD)2PHAL as the catalyst. This methodology is the only example of the catalytic asymmetric construction of spirooxindole 2H-azirine compounds.

Isolation and identification of antioxidant and α-glucosidase inhibitory compounds from fruit juice of Nitraria tangutorum

Nitraria tangutorum Bor., having edible berries, is valued for reputed health benefits in Qinghai-Tibet plateau. The phytochemical research on the fruit juice of N. tangutorum led to the isolation of twenty-six compounds including five new compounds, tangutorids A-D (1, 2, 3a, and 3b), and (3E,5E)-7-O-β-glucosyl-4-(2-methoxy-2-oxoethyl)hepta-3,5-dienoic acid (15). The structures of these compounds were elucidated through comprehensive spectroscopic analyses. Tangutorids A-F were the first examples of glucose-derived β-carbolines from natural products. The biogenetic pathways of 1-8 were proposed to involve Pictet-Spengler reactions and described starting from the co-isolated tryptophan (10) and corresponding aldehydes. All isolates were evaluated for their antioxidant and α-glucosidase inhibitory activities. Compounds 21, 22, and 24 showed antioxidant activity with SC50 values ranging from 12.2±1.9 to 30.4±2.7μg/mL, and compound 1 showed strong α-glucosidase inhibitory effect with IC50 value of 63.3±4.6μg/mL.